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#include<bits/stdc++.h>

#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define FORD(i, a, b) for(int i = (a); i >= (b); --i)
#define VAR(v, i) __typeof(i) v=(i)
#define FORE(i, c) for(VAR(i, (c).begin()); i != (c).end(); ++i)


#define VI vector<int>
#define PII pair<int,int>
#define st first
#define nd second
#define mp make_pair
#define pb push_back
#define lint long long int


#define debug(x) {cerr <<#x <<" = " <<x <<endl; }
#define debug2(x,y) {cerr <<#x <<" = " <<x << ", "<<#y<<" = "<< y <<endl; }
#define debug3(x,y,z) {cerr <<#x <<" = " <<x << ", "<<#y<<" = "<< y << ", " << #z << " = " << z <<endl; }
#define debugv(x) {{cerr <<#x <<" = "; FORE(itt, (x)) cerr <<*itt <<", "; cerr <<endl; }}
#define debugt(t,n) {{cerr <<#t <<" = "; FOR(it,0,(n)) cerr <<t[it] <<", "; cerr <<endl; }}


#define make( x) int (x); scanf("%d",&(x));
#define make2( x, y) int (x), (y); scanf("%d%d",&(x),&(y));
#define make3(x, y, z) int (x), (y), (z); scanf("%d%d%d",&(x),&(y),&(z));
#define make4(x, y, z, t) int (x), (y), (z), (t); scanf("%d%d%d%d",&(x),&(y),&(z),&(t));
#define IOS ios_base::sync_with_stdio(0)
#define HEAP priority_queue


#define read( x) scanf("%d",&(x));
#define read2( x, y) scanf("%d%d",&(x),&(y));
#define read3(x, y, z) scanf("%d%d%d",&(x),&(y),&(z));
#define read4(x, y, z, t) scanf("%d%d%d%d",&(x),&(y),&(z),&(t));


using namespace std;

int n;
int mod = 998244353;
char s[50005];

int dp[50005];
int last[10];
int od_ost[10][10];

void doit() {
	FOR(i,0,6) last[i] = -1;
	FOR(i,0,6) FOR(j,0,6) od_ost[i][j] = -1;

	dp[0] = 1;
	FOR(i,1,n+1) {
		dp[i] = 2 * dp[i-1];
		int lst = last[s[i-1]-'a'];
		if (lst != -1) {
			dp[i] = dp[i] - dp[lst];
		}	
		last[s[i-1]-'a'] = i - 1;
	
		if (dp[i] < 0) dp[i] += mod;
		if (dp[i] >= mod) dp[i] -= mod;
	}

	int TOTAL = dp[n] - 1;
	//cout << "TOTAL " << TOTAL << endl;
	
	dp[0] = 1;
	FOR(i,0,6) {
		od_ost[i][s[0]-'a'] = 0;
	}
	FOR(i,1,n) {
		int ja = s[i]-'a';
		dp[i] = 0;
		if (od_ost[ja][ja] == -1) dp[i] = 1;
		FOR(j,0,6) {
			if (od_ost[ja][j] != -1) 
				dp[i] = (dp[i] + dp[od_ost[ja][j]]) % mod;
		}
		FOR(j,0,6) {
			od_ost[ja][j] = -1;
			od_ost[j][ja] = i;
		}
	}
/*	FOR(i,0,n) {
		cout << dp[i] << " " ;
	}
	cout << endl; */
	int UNIQUE = 0;
	FOR(j,0,6) {
		if (od_ost[j][j] != -1) 
			UNIQUE = (UNIQUE + dp[od_ost[j][j]]) % mod;
	}
//	cout << "UNIQUE : " << UNIQUE << endl;
	int res = (TOTAL - UNIQUE + mod)%mod;
	printf("%d\n", res);
}

void solve() {
	read(n);
	make(q);
	scanf("%s", s);
	doit();
	FOR(i,0,q) {
		make(pos); pos--;
		char C = 'A'; 
		while (C<'a' || C > 'f') C = getchar();
		s[pos] = C;
		doit();
	}
}


int main() {
	solve();
}